■ 
frequency of the marrow cells following in vitro exposure to the MDR 
viruses before transplant. These studies have also shown that the 
retroviruses is functional by the criterion of resistance to the 
bacterial resistance gene Neo. The presence of the retroviral 
transgenome in the cells has persisted up to 9-12 months. We have 
recently shown that we can achieve higher than 10% transduction 
frequency if we use stromal monolayers to support the growth of the 
hematopoietic cells during the transduction (19) . 
Interestingly, the studies of Brenner have been positive, the AML 
cells of these patients are also positive at the 10% level at the time 
of relapse, suggesting that all of the cells of marrow exposed to the 
safety-modified retroviruses are modified at the same level with the 
vector sequences. The data and our animal model data suggests that well 
will be able to modify the normal hematopoietic stem cells of these ! 
patients with the retroviruses which are safety-modified and contain i 
a functional transcription unit with MDR-1 cDNA. 
Accordingly, we have proposed to modify the marrow cells of refractory 
ovarian cancer patients, whose expectation of dying from the disease 
(by virtue of adverse prognostic features) is 80% or more. In this 
program, we will harvest the marrow following conventional dose 
chemotherapy, purify the early progenitor cells through CD34 
selection, and then modify the marrow cells with a protocol outlined 
in Appendix D. We will then treat the systemic disease with a regimen 
which consists of high dose cyclophosphamide (1.7 g/m 2 /d x 3) and 
thiotepa (225 mg/m 2 /d x 3) . This regimen was chosen as it has two 
alkylating agents which are active in ovarian cancer, and at the same 
time will provide suppression of the endogenous hematopoiesis needed 
to facilitate engraftment of the genetically-modified cells. These 
patients will be transplanted with the genetically modified stem 
cells. Following recovery of hematopoietic function, the patients 
will receive cyclical Taxol therapy with starting doses at 135 mg/m 2 . 
The dose will be increased by 50 mg/m 2 every course until toxicity is 
encountered. The courses will be delivered every three to four weeks, 
depending on recovering the ANC to 2000/mm 3 and the platelet amount to 
100,000/mm 3 . We will measure the levels of the cells which are 
modified by the MDR-1 viruses, and monitor the rate of hematopoietic 
recovery, which should become more rapid with each cycle and should 
contain higher and higher percentages of MDR-1 cDNA positive cells due 
to the selective effect of the chemotherapy. Finally, once this 
principle of in vivo selection is established, it will be possible to 
increase the doses of Taxol with each cycle of therapy. The goal of 
this program is to establish this principle of in vivo selection of 
genetically modified cells, and to study their effect on the ability 
to deliver very intensive doses of combination chemotherapy, or at 
least in the initial phases, relatively intensive doses of Taxol 
following recovery of hematopoietic function after autologous bone 
marrow transplantation. This may have a beneficial effect on the 
survival of these patients in whom the inability to eradicate residual 
disease lead to an 80% expectation of dying of their disease within 
two years. 
3.0 BACKGROUND DRUG INFORMATION (SEE APPENDIX C) 
Recombinant DNA Research, Volume 17 
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